1. Field of the Invention
The present invention relates to a slider used in a hard disc drive or the like and a method of producing the slider, and in particular, to the structure of a protective film formed on a air bearing surface of the slider and a method of forming the same.
2. Description of the Related Art
A magnetic head slider (hereinafter referred to as slider) may make contact with a recording medium (magnetic disk) in a hard disc drive, for example at the time of starting the drive employing a contact start/stop method or at the time that a hard disc is subjected to external shock while in operation. A protective film composed of diamond like carbon (DLC) or the like for preventing the slider from making contact is formed on the air bearing surface (ABS) of the slider. Similarly, a protective film composed of DLC or the like is formed on a recording layer of the recording medium.
The DLC film formed on the air bearing surface is formed using a thin film forming technique such as sputtering or vapor deposition. Since the surface of substrate made of Al2O3—TiC-based ceramics (AlTic) which is the principal material of the slider is heated when the film is formed, the DLC film is distorted by the difference in the thermal expansion coefficient between the substrate and the DLC film when the film is cooled after being formed. Because the DLC film is high in hardness (high rigidity), it is subjected to larger internal stress (contraction stress) than film made of a different material if both films are distorted to the same degree. Therefore, even a small shock will likely cause the DLC film to release internal stress and cause it to peel off from the substrate. Since the DLC film does not have enough adhesive force to the AlTic substrate, an intermediate layer (adhesive layer) consisting of Si (silicon) or the like is generally provided beneath the DLC film. That is set forth, for example, in Japanese Patent Laid-Open No. H04-364217, H10-3630, 2001-266324 and 2000-222714.
Incidentally, it has been known that DLC largely changes in strength such as hardness and toughness with the addition or the reduction of hydrogen. Japanese Patent Laid-Open No. H10-3630 and 2001-266324 have disclosed proposals in which a multi-layer structure DLC film with excellent functions can be formed by varying the conditions for forming a film when DLC is used as a protective film of the slider.
Japanese Patent Laid-Open No. 2000-222714 has proposed a method of producing a pad consisting of DLC formed on the air bearing surface. This publication has disclosed a technique in which a material substance of the pad is deposited by vapor deposition at a tilted angle with respect to a line normal to the air bearing surface when the DLC film is deposited using filtered cathodic arc vapor deposition (FACVD or FCVA).
The protective film based on conventional art described above has no problem in terms of its performance as the protective film for the slider, however, it has the following other problems. First, two or more targets are required because a material entirely different from DLC is used in the intermediate layer (adhesive layer). This increases the cost because the structure of a film forming device is complicated or two film forming devices are required. The adoption of multi-layer structure DLC film as disclosed in Patent Document 2 requires at least three layers made of the intermediate layer (adhesive layer) and multi-layer structure DLC layers, and therefore the film can be totally thickened. This makes it difficult to decrease the distance between a magnetic head (a writing element and a reading element) and the recording layer of the recording disc (so-called a distance of magnetic space), which becomes a hindrance to increasing recording density.